Members of the military, law enforcement and other such entities greatly benefit from experiencing training exercises which are as close to real-life combat as possible in order to better hone both their marksmanship and tactical strategy. Thus, many such institutions utilize reduced energy, training products which permit the simulation of a “live fire” event without the risks associated with using conventional live ammunition. Such products can include converted or dedicated automatic or semi-automatic straight blowback operated firearms used to fire the reduced energy ammunition. Being able to employ an individual's own service-issued firearm in such training exercises brings added realism to each scenario. The projectiles fired from such modified firearms tend to include some sort of marking substance, i.e., paint or dye, a blank or a short range target projectile. In addressing the needs of the users of such systems, various inventors have provided solutions allowing the conversion of service-issued firearms to fire reduced energy training cartridges with varying success.
In general, the reduced energy ammunition of the prior art employs a two-piece casing within which the projectile is seated. The first portion of the cartridge is a case which typically resembles the rearward portion of a conventional round of ammunition. The second portion is a sabot which is typically inserted into the first portion and serves to channel a controlled amount of gas pressure from the cartridge explosive charge toward the projectile. The total cartridge explosive charge is the sum of charge contained in the primer and the propellant powder, if such powder is used. Depending on the type of primer selected, it is possible to operate reduced energy ammunition on the primer charge alone.
Examples of such cartridges are shown in U.S. Pat. No. 6,575,098 to Hsiung and U.S. Pat. No. 5,395,937 to Dittrich. While the ammunition disclosed in these and other references are adequate for the desired purpose, there are several shortcomings present in the prior art which the present invention seeks to address.
First, the design of reduced energy ammunition casings in the prior art are often made of conventional cartridge brass. Cartridge brass is typically employed in the manufacturing of thin walled casings with folded mouth designs because of its malleability and relative strength-to-thickness ratio gained through cold working. However, cartridge brass is relatively expensive for reduced energy cartridge case application when compared with alternative materials such as aluminum alloys, zinc alloys, other alloys, steel or even polymers. The use of such alternative materials tends to reduce the raw material and manufacturing costs, but generally requires the ammunition casing itself to be thicker due to the decrease in physical strength associated with these materials as well as to facilitate associated high volume manufacturing processes.
It is noted that the of use polymer casings is hinted at in the prior art, however polymers are not generally a good choice for the casing material for several reasons. First, their lack of compressive strength results in an inability to retain a press-fitted primer. Also, the relatively low tensile strength of polymer casings makes it difficult for them to resist and contain gas pressure of the application. Additionally, the use of polymers in the sabot cartridge component involves significant design challenges with regard to the impact, compressive, tensile and shearing strength, etc., of such materials when exposed to the stresses present when the ammunition is assembled, stored or fired over the ammunition's standard application temperature range which can vary by as much as 72° C. Such design implications and solutions for the same are not discussed in the prior art. Thus, when using alternative materials in a reduced energy training cartridge there exists a need for a design which permits safe, consistent operation of the ammunition while simultaneously being able to utilize comparatively inexpensive materials.
Second, many existing designs for reduced energy training ammunition contain complex designs which add to manufacturing delays and increased production complexity. For example, U.S. Pat. No. 6,575,098 to Hsiung requires the forward portion of the casing to have an internal groove and have a spring-like component inserted during manufacture. Additionally, other known designs employ rubber gaskets in order to provide an acceptable gas seal between the two metallic casing components. Thus, there exists a need for a reduced energy training round which employs inexpensive materials while simultaneously providing a simple and robust design which can easily be manufactured on a large scale.